Thin film capacitor and method for manufacturing the same

ABSTRACT

The present invention comprises the steps of (a) forming a first electrode on a substrate via an adhesion enhancing layer, (b) forming a capacitor insulating film containing a laminated film, in which an amorphous dielectric film and a polycrystalline dielectric film are laminated via a wave-like interface, by forming sequentially and successively the amorphous dielectric film and the polycrystalline dielectric film made of same material on the first electrode, (c) forming a second electrode on the capacitor insulating film, and (d) a step of annealing the capacitor insulating film in an oxygen atmosphere.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority of Japanese PatentApplication No. 2002-83315, filed on Mar. 25, 2002, the contents beingincorporated herein by reference. This is a division of Ser. No.10/940,605 filed on Sep. 15, 2004, which is a division of Ser. No.10/365,478 filed on Feb. 13, 2003, U.S. Pat. No. 6,882,516.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film capacitor and a method ofmanufacturing the same and, more particularly, a thin film capacitorhaving a high-dielectric capacitor insulating film and a method ofmanufacturing the same.

2. Description of the Prior Art

The integrated high-dielectric thin film capacitor is employed as thedecoupling capacitor that suppresses voltage noises or voltage variationcaused in the power bus line, the storage capacitor of DRAM ornonvolatile FRAM (NVFRAM), and the dynamic tunable element inapplications of the microwave devices. In these applications,high-dielectric material or ferroelectric material made of any one ofthe oxide having the perovskite structure such as (Ba,Sr)TiO₃ and thecompound containing the pyrochlore structure such as Pb2(ZrTi)₂O₇ isoften employed as the material of the capacitor insulating film.

However, major reasons for hesitating the employment of these capacitorinsulating films are that the leakage current is large and reliabilityis low at the time of high voltage application.

The electrical characteristics of the capacitor are strongly affected byfilm quality of the dielectric film as the capacitor insulating film,particularly the dielectric oxide thin film. In more detail, normallythe polycrystalline dielectric oxide thin film has a high relativedielectric constant but has a low breakdown voltage. In contrast, theamorphous dielectric oxide thin film has a low relative dielectricconstant but has a high breakdown voltage and a small leakage current.Thus, such thin film can attain the high reliability.

Based on these considerations, in order to compensate thepolycrystalline dielectric oxide thin film and the amorphous dielectricoxide thin film for respective demerits, it may be thought of to employa laminated structure containing both of them. An example of suchlaminated structure is shown in FIG. 1 as a sectional view. In FIG. 1, 1is a silicon substrate, 2 is a silicon oxide film, 3 is a firstelectrode, 4 is an amorphous dielectric oxide thin film, 5 is apolycrystalline dielectric oxide thin film, and 6 is a second electrode.

Such laminated structure can lead to an optimization of the electricalcharacteristics such as the capacitance, the leakage current, thebreakdown voltage, etc. In other words, it can lead to a formation ofthe capacitor with the high breakdown voltage, the small leakagecurrent, and the available capacitance value.

Such laminating method/laminated structure are set forth in U.S. Pat.Nos. 6,190,924B1 and 6,143,597, and Japanese Patent ApplicationPublications (KOKAI) Hei 05-343254, Hei 09-36309, Hei 11-330391,2003-31403, etc. According to these prior arts, the laminated structureis obtained by laminating the flat amorphous dielectric thin film andthe flat polycrystalline dielectric thin film. The flat amorphousdielectric oxide thin film and the flat polycrystalline dielectric oxidethin film are formed of different film forming material under differentfilm forming conditions respectively.

However, according to this laminating method, since the sufficientlyhigh effective dielectric constant cannot be derived yet and also avariety of film forming conditions and film forming materials arerequired, it causes a serious problem such that complexity of theproduction control is increased and thus increase in a production costis brought about. Also, since the film forming conditions and the filmforming materials are different, respective film formations must becarried out while changing the chamber and thus it is possible that theinterface between the amorphous dielectric thin film and thepolycrystalline dielectric thin film is contaminated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thin filmcapacitor capable of achieving a larger relative dielectric constant, ahigher breakdown voltage, and a smaller leakage current whilesimplifying film forming conditions and film forming material to havehigh reliability, and a method of manufacturing the same.

A thin film capacitor set forth in claim 1 of this application,comprises a first electrode formed on a substrate; a capacitorinsulating film containing a laminated film, which is constructed bylaminating an amorphous dielectric film and a polycrystalline dielectricfilm via a wave-like interface, on the first electrode; and a secondelectrode formed on the capacitor insulating film.

According to the thin film capacitor of the present invention, thecapacitor insulating film is constructed by laminating the amorphousdielectric film and the polycrystalline dielectric film via thewave-like interface. Therefore, the breakdown voltage is decided by thelarge film thickness portion of the amorphous dielectric film, and alsoa magnitude of the leakage current is decided by the small filmthickness portion of the amorphous dielectric film. Also, thecapacitance is decided in proportion to an effective film thickness ofthe polycrystalline dielectric film, which is an average film thicknessthereof if the wave-like interface would have been flattened on anaverage.

Meanwhile, in the laminated structure in the prior art, if the filmthickness of the amorphous dielectric film is decided so that thelaminated structure in the prior art has the same breakdown voltage asthe laminated structure of the present invention, the film thickness ofthe polycrystalline dielectric film is reduced much more in thelaminated structure having the flat interface, and thus the effectiverelative dielectric constant is lowered.

In this manner, the capacitor of the present invention having thelaminated structure via the wave-like interface can enhance the relativedielectric constant and can achieve the improvement of the breakdownvoltage, and also can maintain the small leakage current.

According to the experiment made by the inventors of the presentinvention, if the laminated structure of the present invention havingthe wave-like interface and the laminated structure having the flatinterface in the prior art are compared with each other under such acondition that a maximum film thickness of the amorphous dielectric filmhaving the wave-like surface is set equal to the film thickness of theamorphous dielectric film having the flat surface, the capacitor of thepresent invention having the laminated structure via the wave-likeinterface was able to enhance the effective relative dielectric constantand was able to achieve the improvement of the breakdown voltage andalso reduction in the leakage current.

In a thin film capacitor set forth in claim 5 of this application, anadhesion enhancing layer is formed between the substrate and the firstelectrode, and the adhesion enhancing layer consists of a film made ofnoble metal or its alloy, alloy of noble metal and base metal, noblemetal oxide, metal oxide, metal nitride, or mixture containing any twoor more of the noble metal, the alloy, the oxide and the nitride, or amulti-layered film containing any two films or more made of the noblemetal, the alloy, the oxide or the nitride.

According to the thin film capacitor of the present invention, theadhesion enhancing layer for increasing a mutual adhesion strength isformed between the substrate and the first electrode. Therefore,peeling-off of the capacitor from the substrate can be prevented, andalso reliability of the device into which the thin film capacitor isinstalled can be improved.

A method of manufacturing a thin film capacitor set forth in claim 20 ofthis application, comprises the steps of (a) forming a first electrodeon a substrate via an adhesion enhancing layer; (b) forming a capacitorinsulating film containing a laminated film, in which an amorphousdielectric film and a polycrystalline dielectric film are laminated viaa wave-like interface, by forming sequentially and successively theamorphous dielectric film and the polycrystalline dielectric film madeof same material on the first electrode; (c) forming a second electrodeon the capacitor insulating film; and (d) annealing the capacitorinsulating film in an oxygen atmosphere.

According to the present invention, the amorphous dielectric film andthe polycrystalline dielectric film are formed successively by using thesame material under the same film forming conditions. The inventors ofthe present invention have verified experimentally the fact that thelaminated structure having the wave-like interface can be formedaccording to such film formation. In the above film forming method, thegrowth mechanism to be described in the following may be considered.That is, the growth is started at the temperature at which the amorphousdielectric film can be grown. Then, cores of crystals are generated withthe increase in temperature of the growth surface caused by thecollision of the film forming material against the growth surface. Then,crystal grains are grown up from these cores to form the polycrystallinedielectric film. In this case, since the growth of the crystal grainsspreads from the cores of crystals to peripheries, the interface betweenthe amorphous dielectric film and the polycrystalline dielectric film isformed like the wave.

Therefore, since the laminated structure constructed by laminating theamorphous dielectric film and the polycrystalline dielectric film can beformed in the same chamber, contamination of the layer interface in thelaminated structure can be prevented. Also, since the same film formingconditions and the same film forming material can be employed, theproduction control can be simplified and also reduction in theproduction cost can be achieved.

In the method of manufacturing the thin film capacitor set forth inclaim 21 of this application, in the step (b), the amorphous dielectricfilm and the polycrystalline dielectric film are formed successivelywhile heating the substrate at a constant temperature of less than 450°C.

According to the present invention, since the amorphous dielectric filmand the polycrystalline dielectric film are formed successively at aconstant temperature of less than 450° C., the amorphous dielectric filmcan be grown to have an appropriate film thickness. Therefore, as shownin FIG. 3, the result leads to a formation of the laminated structureconsisting of the amorphous dielectric film and the polycrystallinedielectric film and having the wave-like interface between them.

In the method of manufacturing the thin film capacitor set forth inclaim 22 of this application, in the step (b), formation of thelaminated film is executed by an RF magnetron sputter method or a DCsputter method.

The present invention employs the RF magnetron sputter method or the DCsputter method, and thus it is capable of forming the laminatedstructure consisting of the amorphous dielectric film and thepolycrystalline dielectric film and having the wave-like interfacebetween them, as shown in FIG. 3, by the continuous film formation usingthe same film forming material under the same film forming conditions.

In the method of manufacturing the thin film capacitor set forth inclaim 23 of this application, in the RF magnetron sputter method or theDC sputter method in the step (b), the amorphous dielectric film and thepolycrystalline dielectric film are formed successively while keeping atleast a pressure of the sputter gas, a flow rate of the sputter gas, andpower application conditions to the sputter gas constant.

According to the experiment made by the inventors of the presentinvention, in the RF magnetron sputter method or the DC sputter method,if at least the pressure of the sputter gas, the flow rate of thesputter gas, and the power application condition of the sputter gas arekept constant, it can lead to a formation of the laminated structure inwhich the amorphous dielectric film and the polycrystalline dielectricfilm are laminated via the wave-like interface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a structure of an overall capacitorin the prior art;

FIG. 2 is a sectional view showing a structure of an overall capacitorin a first example according to a first embodiment of the presentinvention;

FIG. 3 is a microphotograph showing a cross section of a capacitorinsulating film in FIG. 2;

FIG. 4 is a graph showing measured results of a leakage current densityof the capacitor in FIG. 2;

FIG. 5 is a sectional view showing a structure of an overall capacitorin a second example according to the first embodiment of the presentinvention;

FIG. 6 is a sectional view showing a structure of an overall capacitorin a third example according to the first embodiment of the presentinvention;

FIG. 7 is a sectional view showing an application 1 of a capacitoraccording to a second embodiment of the present invention;

FIG. 8 is a sectional view showing an application 2 of the capacitoraccording to the second embodiment of the present invention; and

FIG. 9 is a sectional view showing an application 3 of the capacitoraccording to the second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained with reference tothe drawings hereinafter.

First Embodiment

FIG. 2, FIG. 5 and FIG. 6 are sectional views showing a structure of acapacitor having a high-dielectric capacitor insulating film as a firstembodiment of the present invention. FIG. 3 is a microphotograph showinga cross section of the formed capacitor insulating film.

As shown in FIG. 2, FIG. 5, or FIG. 6, the capacitor in this embodimenthas a semiconductor substrate 11, an insulating film 12 formed thereon,a first electrode 13 formed on the insulating film 12, a capacitorinsulating film 51 a, 51 b, or 51 c formed on the first electrode 13,and a second electrode 16 formed on the capacitor insulating film 51 a,51 b, or 51 c.

In the capacitor insulating film 51 a, 51 b, 51 c, amorphous dielectricinsulating films 14 a, 14 b, 18 and polycrystalline dielectricinsulating films 15 a, 15 b, 19 are laminated via a wave-like interface.In above Figures, crystal grains are shown by regions that arefractionated by vertical lines in the polycrystalline dielectricinsulating films 15 a, 15 b, 19. Each of crystal grains has a differentcrystal axis, respectively. In the capacitor insulating films 51 a, 51b, 51 c, a minimum film thickness value of the amorphous dielectricinsulating films 14 a, 14 b, 18 is in a range of 1 nm to 100 nm and amaximum film thickness value thereof is in a range of 3 nm to 300 nm.

As shown in FIG. 5 and FIG. 6, normally an adhesion enhancing layer 17is interposed between the insulating film 12 and the first electrode 13to enhance a mutual adhesion.

The semiconductor substrate 11 consists of a silicon (Si) substrate, agermanium (Ge) substrate, a silicon germanium (SiGe) substrate, or agroup III-V compound semiconductor substrate.

Also, the insulating film 12 on the semiconductor substrate 11 consistsof an oxide film, a nitride film, an oxide nitride film, ahigh-dielectric metal oxide film, a xerogel film made of silica or thelike, an insulating film made of mixture containing any two or more ofoxide, nitride, oxide nitride, high-dielectric metal oxide and xerogel,or a multi-layered film containing any two or more of these films.

The adhesion enhancing layer 17 consists of a film made of noble metalor its alloy, alloy of noble metal and base metal, noble metal oxide,metal oxide, metal nitride, or mixture containing any two or more of thenoble metal, the alloy, the oxide and the nitride, or a multi-layeredfilm containing any two or more of films made of the above metal, thealloy, the oxide or the nitride. More particularly, Pt, Ir, Zr, Ti,TiO_(x), IrO_(x), PtO_(x), ZrO_(x), TiN, TiAlN, TaN, TaSiN, or the likemay be employed as the material of the adhesion enhancing layer 17.

The first electrode 13 consists of a conductive film that is made oftransition metal, noble metal or its alloy, alloy of noble metal andbase metal, conductive oxide, or mixture containing any two or more ofthese metals, the alloys and the oxide, or a multi-layered conductivefilm that contains any two films or more made of these metals, thealloys or the oxide. More particularly, a metal such as Pt, Pd, Ir, Ru,Rh, Re, Os, Au, Ag, Cu, etc. and a conductive oxide such as PtO_(x),IrO_(x), RuO_(x), etc. may be employed as the material of the firstelectrode 13.

As the dielectric material of both or any one of the amorphousdielectric films 14 a, 14 b, 18 and the polycrystalline dielectricinsulating films 15 a, 15 b, 19 of the capacitor insulating films 51 a,51 b, 51 c, the perovskite-type oxide having a structural formula ABO₃(where A is at least one positive ion having 1 to 3 positive charges,and B is acidic oxide that contains a metal belonging to a group IVB,group VB, group VIB, group VIIB, or group IB in the periodic table) canbe employed. More particularly, there are (Ba,Sr)TiO₃, PbTiO₃, etc. assuch perovskite-type oxide.

Otherwise, as the dielectric material of both or any one of theamorphous dielectric films 14 a, 14 b, 18 and the polycrystallinedielectric insulating films 15 a, 15 b, 19, the compound containing thepyrochlore structure having a structural formula A₂B₂O_(x) (where A isat least one positive ion having 1 to 3 positive charges, B is acidicoxide that contains a metal belonging to a group IVB, group VB, groupVIB, group VIIB, or group IB in the periodic table, and x is 6 to 7) maybe employed. There is Ti, Zr, Hf, or the like as the group IVB metal inthe periodic table, there is V, Nb, or Ta as the group VB metal, thereis Cr, Mo, W, or the like as the group VIB metal, there is Mn, Re, orthe like as the group VIIB metal, and there is Cu, Ag, Au, or the likeas the group IB metal. Also, particularly there is Pb₂(ZrTi)₂O₇, or thelike as the compound containing such pyrochlore structure.

Further, both or any one of the amorphous dielectric films 14 a, 14 b,18 and the polycrystalline dielectric films 15 a, 15 b, 19 of thecapacitor insulating films 51 a, 51 b, 51 c may be formed of a film thatconsists of any one of dielectric materials of titanate, aluminate,niobate, and tantalate, or a multi-layered film that contains any two ormore of the films made of these dielectric materials.

Otherwise, both or any one of the amorphous dielectric films 14 a, 14 b,18 and the polycrystalline dielectric films 15 a, 15 b, 19 of thecapacitor insulating films 51 a, 51 b, 51 c may be formed of a film thatcontains any one of dielectric materials of barium titanate, strontiumtitanate, barium strontium titanate, tantalum oxide, potassium tantalumoxide, lanthanum aluminate, yttrium aluminate, bismuth titanate,strontium bismuth tantalum oxide, strontium bismuth niobate, strontiumbismuth tantalate niobate, tin zirconate titanate, tin tantalumzirconate titanate, and tin magnesium niobate, or a film that is made ofa mixture which contains two or more of these dielectric materials andinto which a dopant is introduced. As the dopant, Mn, Ni, Fe, or Y isemployed.

The second electrode 16 consists of a conductive film that is made oftransition metal, noble metal or its alloy, alloy of noble metal andbase metal, conductive oxide, or mixture containing any two or more ofthese metals, the alloys and the oxide, or a multi-layered conductivefilm that contains at least a double-layer or more film made of thesemetals, the alloys or the oxide. More particularly, a metal such as Pt,Pd, Ir, Ru, Rh, Re, Os, Au, Ag, Cu, etc. and a conductive oxide such asPtO_(x), IrO_(x), RuO_(x), SrRuO₃, LaNiO₃, etc. may be employed as thematerial of the second electrode 16.

In this case, although not shown, a passivation film is formed on thesecond electrode 16 in some case.

According to the thin film capacitor of the first embodiment of thepresent invention, since the capacitor insulating film is constructed bylaminating the amorphous dielectric film 14 a, 14 b, or 18 and thepolycrystalline dielectric film 15 a, 15 b, or 19 via the wave-likeinterface, the breakdown voltage is decided by the large film thicknessportion of the amorphous dielectric film 14 a, 14 b, or 18 and also amagnitude of the leakage current is decided by the small film thicknessportion thereof. Also, the capacitance is decided in proportion to aneffective film thickness of the polycrystalline dielectric film 15 a, 15b, or 19, which is an average film thickness thereof if the wave-likeinterface would have been flattened on an average.

Meanwhile, in the laminated structure having a flat interface, if thefilm thickness of the amorphous dielectric film is decided so that thelaminated structure in the prior art has the same breakdown voltage asthe laminated structure of the present invention, the film thickness ofthe polycrystalline dielectric film is reduced much more in thelaminated structure having the flat interface, and thus the relativedielectric constant is lowered in the laminated structure in the priorart.

In this manner, the capacitor of the present invention having thelaminated structure via the wave-like interface can enhance theeffective relative dielectric constant and achieve the improvement ofthe breakdown voltage, and also can maintain the small leakage current.

Next, a method of manufacturing the above capacitor will be explainedwith reference to FIG. 2, FIG. 5, and FIG. 6 hereunder.

First, the insulating film 12 is formed on the semiconductor substrate11. If the silicon substrate is employed as the semiconductor substrate,a silicon oxide film is formed by thermally oxidizing a surface of thesilicon substrate. In this case, after this formation and before thefirst electrode 13 is formed, the adhesion enhancing layer 17 may beformed to enhance the adhesion between the insulating film 12 and thefirst electrode 13.

Then, the first electrode 13 is formed on the insulating film 12 and theadhesion enhancing layer 17 by the magnetron sputter method.

Then, the amorphous dielectric film 14 a, 14 b, or 18 and thepolycrystalline dielectric film 15 a, 15 b, or 19 are formedsequentially and successively on the first electrode 13 by using thedielectric material. Thus, it results in a formation of the capacitorinsulating film 51 a, 51 b, or 51 c containing the laminated films,which is composed of the amorphous dielectric film 14 a, 14 b, or 18 andthe polycrystalline dielectric film 15 a, 15 b, or 19 laminated via thewave-like interface.

This film forming step is executed at a predetermined substrate heatingtemperature of less than 450° C. Also, the RF magnetron sputter methodor the DC sputter method may be employed. In these sputter methods,while keeping at least the pressure of the sputter gas, the flow rate ofthe sputter gas, and the power application condition of the sputter gasconstant, the amorphous dielectric film 14 a, 14 b, or 18 and thepolycrystalline dielectric film 15 a, 15 b, or 19 are formedsuccessively.

As the reason why the wave-like interface is formed between theamorphous dielectric film 14 a, 14 b, or 18 and the polycrystallinedielectric film 15 a, 15 b, or 19 respectively, a following mechanismcan be considered. That is, at first the amorphous dielectric film 14 a,14 b, or 18 is formed by starting the growth at a low temperature atwhich the amorphous dielectric film 14 a, 14 b, or 18 can be grown.Then, cores of crystals are generated with the increase in temperatureof the growth surface caused by the collision of the film formingmaterial against the growth surface. Then, crystal grains are grown upfrom these cores to form the polycrystalline dielectric film 15 a, 15 b,or 19. In this case, since the growth of the crystal grains spreadsgradually from the cores of crystals to peripheries, the interfacebetween the amorphous dielectric film 14 a, 14 b, or 18 and thepolycrystalline dielectric film 15 a, 15 b, or 19 is formed like thewave.

Also, since the substrate heating temperature is set to a constanttemperature of less than 450° C., the amorphous dielectric film 14 a, 14b, or 18 can be grown to have an appropriate film thickness. The initialgrowth temperature is decided by the substrate heating temperature, anda film thickness of the amorphous dielectric film 14 a, 14 b, or 18 isformed thicker as this temperature is set lower.

Then, the second electrode 16 is formed on the capacitor insulating film51 a, 51 b, or 51 c.

Then, in order to recover the oxygen defect that is caused in thepolycrystalline dielectric film 15 a, 15 b, or 19 by the sputterparticles when the second electrode 16 is formed, the capacitorinsulating film 51 a, 51 b, or 51 c is annealed in a temperature rangeof 300 to 600° C. for 15 to 30 minute in the oxygen atmosphere. A lowerlimit of 300° C. in the annealing temperature is set as a lower limittemperature that can achieve effectively the recovery of the oxygendefect. An upper limit of 600° C. is set because there is such apossibility that the amorphous film is converted into thepolycrystalline film if the annealing temperature exceeds such upperlimit.

In this case, the final annealing process can be omitted as the case maybe. The annealing process can be omitted in the case where the capacitorof the present invention is employed for the application in which thevoltage is applied while setting the polycrystalline side to a positivepotential and setting the amorphous side to a negative potential. Inthis case, the electrons move from the amorphous side to thepolycrystalline side. Hence, it is the interface between the amorphousdielectric film 14 a, 14 b, or 18 and the underlying first electrode 13that dominates the leakage current. The barrier of this interface isvery high since one side of the interface is formed of the amorphoussubstance, so that the sufficiently good leakage characteristic can beessentially obtained. As a result, the annealing process to be executedafter the film formation can be omitted. On the contrary, if thecapacitor of the present invention is applied to the storage capacitorof DRAM, the polycrystalline side is set to the positive potential aswell as the negative potential and also the amorphous side is set to thenegative potential as well as the positive potential. In this case,since the interface between the polycrystalline dielectric film 15 a, 15b, or 19 and the overlaying second electrode 16 dominates the leakagecurrent, crystallinity of the polycrystalline dielectric film 15 a, 15b, or 19 becomes an important matter. As a result, the annealing processcannot be omitted.

With the above, a capacitor 101 a, 101 b, or 101 c is completed. Then, apassivation film for covering the capacitor 101 a, 101 b, or 101 c maybe formed if necessary.

As described above, according to the method of manufacturing the thinfilm capacitor in the first embodiment of the present invention, theamorphous dielectric film 14 a, 14 b, or 18 and the polycrystallinedielectric film 15 a, 15 b, or 19 are formed successively by using thesame material under the same film forming conditions.

Therefore, the laminated structure in which the amorphous dielectricfilm and the polycrystalline dielectric film are laminated via thewave-like interface can be formed. In this case, contamination of thelayer interface in the laminated structure can be prevented since thesefilms are formed successively in the same chamber, and alsosimplification of the production control and reduction in the productioncost can be achieved since the same film forming conditions and the samefilm forming material can be employed.

First Example

Next, a structure of the capacitor 101 a as a first example of thepresent invention will be explained with reference to FIG. 2 and FIG. 3hereunder.

FIG. 2 is a view showing a sectional structure of the capacitor 101 a asthe first example of the present invention. FIG. 3 is a microphotographshowing a cross section of the capacitor insulating film that isexamined through a microscope.

As shown in FIG. 2, the capacitor 101 a was formed on the silicon oxidefilm 12 overlaying the silicon substrate 11.

As the dielectric material of the capacitor insulating film 51 a, bariumstrontium titanium oxide (abbreviated to “BSTO” hereinafter) wasemployed. As the method of forming the capacitor insulating film 51 a,the RF magnetron sputter method was employed. As the film formingconditions, the substrate heating temperature was set constant as 250°C., the RF power was set to 100 W, the Ar/O₂ ratio was adjusted to30/3.7 by adding O₂ to Ar as the sputter gas, and the gas pressure wasset to 10 mTorr.

As shown in FIG. 3, it was found that, in the formed laminatedstructure, the amorphous dielectric film 14 a and the polycrystallinedielectric film 15 a are laminated via the wave-like interface. A totalfilm thickness was about 100 nm. In such thickness, a minimum filmthickness of the amorphous dielectric film 14 a was almost 10 nm and amaximum film thickness thereof was almost 30 nm. Also, according toanother examination, a Sr containing rate (23%) of the amorphousdielectric film 14 a was slightly smaller than that (26%) of thepolycrystalline dielectric film 15 a.

Then, the relative dielectric constant ε, the capacitance C (μF/cm²) perunit area, the leakage current density J_(L) (A/cm²), and the dielectricbreakdown field strength E_(br) (V/cm) of the above capacitor 101 a weremeasured respectively.

The relative dielectric constant ε was about 50, the capacitance C perunit area was about 0.44 μF/cm², and the dielectric breakdown fieldstrength E_(br) was in excess of 3 MV/cm.

Also, FIG. 4 is a graph showing measured results of the leakage currentdensity with respect to the applied voltage. In FIG. 4, an ordinatedenotes the leakage current density J_(L) (A/cm²) in a logarithmicscale, and an abscissa denotes the applied voltage (V) in a linearscale. According to the measured results, the leakage current densityJ_(L) was about 10⁻¹⁰ A/cm² at the applied voltage of 4 V, and thus thevery small value of J_(L) was obtained.

Second Example

Next, a structure of the capacitor 101 b as a second example of thepresent invention will be explained with reference to FIG. 5 hereunder.FIG. 5 is a view showing a sectional structure of the capacitor 101 b asthe second example of the present invention.

A difference from the first example is that the adhesion enhancing layer17 was formed between the silicon oxide film 12 on the silicon substrate11 and the first electrode 13. As the material of the adhesion enhancinglayer 17, a TiO₂ film was employed. Then, a further difference from thefirst example is that a film thickness of the amorphous dielectric film14 b of the capacitor insulating film 51 b was formed thin. A minimumfilm thickness of the amorphous dielectric film 14 b was almost 1 nm,and a maximum film thickness thereof was almost 10 nm. The reason whythe film thickness of the amorphous dielectric film 14 b was formed thinis that, since the substrate heating temperature during the filmformation was set higher than the first example such as 300° C., thetemperature of the film forming surface was increased from the amorphousgrowth temperature to the polycrystalline growth temperature at itsearly stage of the film formation.

A film thickness of the overall capacitor insulating film 51 b is set tothe same thickness as the first example and was about 100 nm.

Then, the relative dielectric constant ε, the capacitance C (μF/cm²) perunit area, the leakage current density J_(L) (A/cm²), and the dielectricbreakdown field strength E_(br) (V/cm) of the capacitor 101 b formed asabove were measured respectively.

The relative dielectric constant ε was about 80, the capacitance C perunit area was about 0.71 μF/cm², and the dielectric breakdown fieldstrength E_(br) was more than 2 MV/cm. Also, the leakage current densityJ_(L) was about 10⁻⁹ A/cm² at the applied voltage of 4 V. Since the filmthickness of the amorphous dielectric film 14 b of the capacitorinsulating film 51 b was formed thin rather than the first example, thedielectric breakdown field strength E_(br) was lowered and also theleakage current density J_(L) was increased slightly, nevertheless bothcharacteristics were kept at a very good level rather than the laminatedstructure that has the flat interface in the prior art.

Third Example

Next, a structure of the capacitor 101 c as a third example of thepresent invention will be explained with reference to FIG. 6 hereunder.FIG. 6 is a view showing a sectional structure of the capacitor 101 c asthe third example.

Differences from the first example reside in that strontium titaniumoxide (STO) was employed as the dielectric material of the capacitorinsulating film 51 c and the laminated structure in which the amorphousSTO film 18 and the polycrystalline STO film 19 were laminated via thewave-like interface was employed as the capacitor insulating film 51 c.The film formation of the capacitor insulating film 51 c was executed byusing the strontium titanium as a target and then sputtering the targetby the gas in which O₂ is added to the sputter gas Ar.

Then, the relative dielectric constant ε, the leakage current densityJ_(L) (A/cm²), and the dielectric breakdown field strength E_(br) (V/cm)of the above capacitor 101 c were measured respectively.

The relative dielectric constant ε was 35, and the dielectric breakdownfield strength E_(br) was more than 3 MV/cm. Also, the leakage currentdensity J_(L) was about 10⁻¹⁰ A/cm² at the applied voltage of 4 V, whichis the very small value that is at the same level as the first example.

As described above, according to the capacitors 101 a, 101 b, 101 caccording to the first to third examples, the relative dielectricconstant can be enhanced and also reduction in the leakage current andimprovement in the dielectric breakdown field strength can be achievedin comparison with the laminated structure that has the flat interfacein the prior art.

In this case, in the above first to third examples, both the amorphousdielectric film and the polycrystalline dielectric film were formed ofthe same dielectric material. But different dielectric materials may beemployed.

Second Embodiment

Next, applications of a thin film capacitor according to a secondembodiment of the present invention will be explained with reference toFIG. 7, FIG. 8, and FIG. 9 hereinafter. FIG. 7, FIG. 8, and FIG. 9 aresectional views showing the application of the thin film capacitoraccording to the second embodiment respectively.

In FIG. 7, two thin film capacitors 101 d, 101 e are connected inseries. Two thin film capacitors 101 d, 101 e are put on separateconductive film patterns 22 a, 22 b, which are isolated electrically,respectively and are fixed thereto by the conductive adhesive. In orderto connect two thin film capacitors 101 d, 101 e in series, an upperelectrode of one thin film capacitor 101 d are connected via a wire 23 ato the conductive film pattern 22 b, on which the other thin filmcapacitor 101 e is put and which is connected to a lower electrode ofthereof.

In FIG. 8, two thin film capacitors 101 f, 101 g are connected inparallel. Two thin film capacitors 101 f, 101 g are put on oneconductive film pattern 22 c respectively and are fixed thereto by theconductive adhesive. In order to connect two thin film capacitors 101 f,101 g in parallel, an upper electrode of one thin film capacitor 101 fand an upper electrode of the other thin film capacitor 101 g areconnected via a wire 23 b.

FIG. 9 shows an example in which a capacitor 101 h having the samestructure as the first embodiment is inserted in parallel with outputterminals of a power supply 31 in an AC power supply circuit 102 and isused as the by-pass capacitor. This capacitor 101 h has a function ofeliminating the high-frequency noises generated from the electronicdevice, etc. that are connected to the AC power supply circuit 102. Thiscapacitor 101 h is installed into the semiconductor integrated circuitin which the AC power supply circuit 102 is integrated.

Also, this capacitor may be employed as the capacitor that is installedinto the multi-chip module, or the storage capacitor of DRAM (DynamicRandom Access Memory) and FRAM (Ferroelectric Random Access Memory).

With the above, the present invention is explained particularly withreference to the embodiment. But the present invention is not limited tothe examples that are shown in the above embodiments, and variations ofthe above embodiments within a range that does not depart from the gistof the present invention may be contained in a scope of the presentinvention.

As described above, according to the thin film capacitor of the presentinvention, since the capacitor insulating film is constructed bylaminating the amorphous dielectric oxide insulating film and thepolycrystalline dielectric oxide insulating film via the wave-likeinterface, the dielectric breakdown voltage is decided by the thickportion of the amorphous dielectric oxide insulating film and alsomagnitude of the leakage current is decided by the thin portion thereof.Also, the relative dielectric constant is decided in proportion to theeffective film thickness of the polycrystalline dielectric oxideinsulating film, which is an average film thickness thereof if thewave-like interface would have been flattened on an average. Therefore,in contrast to the laminated structure having the flat interface in theprior art, the effective relative dielectric constant can be increased,and improvement in the breakdown voltage can be achieved, and the smallleakage current can be maintained.

Also, according to the method of manufacturing the thin film capacitorof the present invention, the amorphous dielectric oxide insulating filmand the polycrystalline dielectric oxide insulating film are formedsuccessively by using the same material under the same film formingconditions. Therefore, the contamination of the layer interface in thelaminated structure can be prevented since the laminated structure canbe formed by laminating the amorphous film and the polycrystalline filmin the same chamber, and also simplification of the production controland reduction in the production cost can be achieved since the same filmforming conditions and the same film forming material can be employed.

1. A method of manufacturing a thin film capacitor, comprising the stepsof: (a) forming a first electrode on a substrate via an adhesionenhancing layer; (b) forming a capacitor insulating film containing alaminated film, in which an amorphous dielectric film and apolycrystalline dielectric film are laminated via a wave-like interface,by forming sequentially and successively the amorphous dielectric filmand the polycrystalline dielectric film made of same material on thefirst electrode; (c) forming a second electrode on the capacitorinsulating film; and (d) annealing the capacitor insulating film in anoxygen atmosphere.
 2. A method of manufacturing a thin film capacitor,according to claim 1, wherein, in the step (b), the amorphous dielectricfilm and the polycrystalline dielectric film are formed successivelywhile heating the substrate at a constant temperature of less than 450°C.
 3. A method of manufacturing a thin film capacitor, according toclaim 1, wherein, in the step (b), formation of the laminated film isexecuted by an RF magnetron sputter method or a DC sputter method.
 4. Amethod of manufacturing a thin film capacitor, according to claim 3,wherein, in the RF magnetron.